Sciatica

What is it?

The sciatic nerve is one of the thickest nerves in the body. It is formed by nerve roots that leave the lower spine, runs through the buttock and down the back of the thigh, and divides just above the knee into branches that continue to the foot. Sciatica is pain that spreads along this path when the nerve, or the roots that form it, are irritated or compressed.

Doctors often call this lumbar radiculopathy (pain arising from a nerve root in the lower back and spreading into the leg). In sciatica the leg pain is usually more troublesome than the back pain, which helps to distinguish it from back pain caused by the muscles alone.

The path the pain takes depends on which nerve root is affected. When the L5 root is involved, pain and numbness usually spread down the outer side of the leg to the top of the foot and the big toe. With the S1 root, pain tends to travel down the calf to the heel and the outer edge of the foot.

What causes it?

Sciatica is a symptom, and treatment is planned around its cause. The most common causes are:

• Lumbar disc herniation: disc material pressing on or irritating a nerve root is the most frequent cause. See lumbar disc herniation for more detail.
• Foraminal narrowing and spinal stenosis: age-related narrowing of the openings the nerve roots pass through, or of the spinal canal itself (spinal stenosis).
• Spondylolisthesis: one vertebra slipping forward over the one below.
• Compression in the buttock: irritation of the nerve around the piriformis muscle is a less common cause.
• Rare causes: infection, tumours or injury.

Not all leg pain is sciatica. Hip joint problems, narrowed leg arteries and muscular pain can cause similar symptoms, which is why an accurate diagnosis comes before treatment.

How is it diagnosed?

The key steps are a careful history and a neurological examination. The path the pain follows down the leg, where sensation is reduced, and changes in muscle strength and reflexes indicate which nerve root is involved. Tests such as the straight leg raise can reveal tension on the nerve root. The hip joint and the circulation in the legs are also checked, because problems in these areas can mimic sciatica.

For recent sciatica without warning signs, scans are often unnecessary. An MRI is requested if symptoms do not ease within a few weeks, if there is weakness, or if an interventional treatment is being considered. EMG may be used when the degree of nerve damage needs to be assessed.

Treatment options

Sciatica settles on its own within a few weeks to a few months in many people. During that time, the aim is to control pain while keeping you moving.

Conservative care

• Keeping active: bed rest does not speed up recovery. Short walks and a gradual return to everyday activities are recommended.
• Exercise and physiotherapy: tailored programmes that strengthen the trunk and improve flexibility.
• Medication: short courses of anti-inflammatory painkillers can be used. In sciatica, nerve pain medicines and long-term strong painkillers offer limited benefit and carry a real risk of side effects, so medicines are chosen with care.

Interventional pain treatments

For severe sciatica that limits daily life, the following may be considered:

• Epidural steroid injection: medication is delivered around the affected nerve root under fluoroscopy (live X-ray). Particularly in recent, severe sciatica, it can reduce pain and make it easier to take part in rehabilitation.
• Non-surgical lumbar disc treatment: when sciatica is caused by a suitable disc herniation, procedures inside the disc are assessed within this approach.
• Radiofrequency treatment: pulsed radiofrequency may be an option for selected patients with long-standing nerve root pain.

In suitable patients these treatments can provide a meaningful reduction in pain. How long the effect lasts varies between individuals, and the risks of each procedure are discussed in detail beforehand.

When is surgery considered?

If pain and loss of function persist despite non-surgical treatment and the imaging findings match the symptoms, surgery to relieve pressure on the nerve (decompression) is assessed with a neurosurgeon or an orthopaedic spine surgeon. Cauda equina syndrome and rapidly progressing weakness need emergency surgical assessment.

When should you see a doctor?

See a doctor if your leg pain is not easing after a few weeks, is getting worse, or is accompanied by new numbness or weakness. An algology (pain medicine) specialist will assess which nerve root the pain is coming from and plan the treatment options with you; you can request an appointment through our contact page.